Amplitude Modulation of Electromagnetic Signals

Abstract

A system and a method are provided to amplitude modulate electromagnetic signals, wherein the system comprising at least one antenna coupled to a respective non-linear load configured to be provided with modulating signals, and wherein the electromagnetic signals are amplitude modulated in accordance with impedance matching between the at least one antenna and its respective load.

Claims

1. A system configured to amplitude modulate electromagnetic signals, wherein said system comprising at least one antenna coupled to a respective load configured to be provided with modulating signals, and wherein said electromagnetic signals are amplitude modulated in accordance with impedance matching between the at least one antenna and its respective load.

2. The system of claim 1, wherein the load of the at least one antenna is a non-linear load which is DC biased by the modulating signals.

3. The system of claim 1, wherein the load of the at least one antenna is a metal-insulator-metal (MIM) load.

4. The system of claim 1, wherein the electromagnetic signals are optical signals.

5. The system of claim 1, further comprising a waveguide for conveying the electromagnetic signals along a pre-defined path.

6. The system of claim 5, wherein said system comprising a plurality of antennas each coupled to a respective MIM load, and wherein said plurality of antennas are arranged serially along the waveguide, and wherein the same modulating signal is applied to each of said MIM loads, thereby enabling serially modulating the electromagnetic signals as they propagate through said waveguide, by the plurality of antennas.

7. A system configured to amplitude modulate electromagnetic signals, wherein said system comprising a plurality of antennas each coupled to a respective MIM load and configured to be provided with a respective modulating signal, and wherein each of the respective modulating signals is applied to each of the MIM loads, thereby obtaining amplitude modulation of the electromagnetic signals in accordance with impedance matching between each of the plurality of antennas and its respective load.

8. The system of claim 7, wherein the plurality of antennas are arranged along a waveguide and the system is configured to enable modulation of the electromagnetic signals by the plurality of antennas, as the electromagnetic signals propagate along said waveguide.

9. The system of claim 7, wherein at least two of the modulating signals provided to said plurality of antennas, are different from each other.

10. The system of claim 7, wherein the load coupled to each of said plurality of antennas is a non-linear load which is DC biased by the respective modulating signal provided to each of said plurality of antennas.

11. The system of claim 7, wherein the electromagnetic signals are optical signals.

12. A method for affecting amplitude modulation onto electromagnetic signals, wherein the method comprising the steps of: providing at least one antenna coupled to a respective load; providing modulating signals to the at least one respective load, for enabling amplitude modulation of the electromagnetic signals; amplitude modulating the electromagnetic signals in accordance with impedance matching between the at least one antenna and its respective load.

13. The method of claim 12, wherein the step of modulating said electromagnetic signals comprises applying a non-linear load which is DC biased by the modulating signals to the respective load of the at least one antenna.

14. The method of claim 12, wherein said respective load of the at least one antenna is a metal-insulator-metal (MIM) load.

15. The method of claim 12, wherein the electromagnetic signals are optical signals.

16. The method of claim 12, wherein a plurality of antennas are provided, each coupled to a respective MIM load, wherein said plurality of antennas are arranged in a serial configuration along a waveguide, and wherein said step of amplitude modulating said electromagnetic signals comprises applying the same modulating signal to each of said respective MIM loads, thereby enabling serially modulating the electromagnetic signals as they propagate through said waveguide, by the plurality of antennas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated herein and constitute a part of this specification, illustrate several embodiments of the disclosure and, together with the description, serve to explain the principles of the embodiments disclosed herein.

[0041] FIG. 1 is a schematic representation of a prior art circuit exemplifying a typical RF AM modulator;

[0042] FIG. 2 is a schematic illustration exemplifying a typical prior art OOK transmitter;

[0043] FIG. 3 illustrates an antenna loaded with a perfect open or short load;

[0044] FIG. 4 illustrates an antenna loaded with a perfectly matched load;

[0045] FIG. 5 illustrates a typical differential resistance of a MIM structure, versus its DC bias voltage;

[0046] FIG. 6 illustrates a system construed in accordance with an embodiment of the invention, for carrying out an amplitude modulation by using a single antenna coupled to a MIM load; and

[0047] FIG. 7 demonstrates a system construed in accordance with another embodiment of the invention, for carrying out an amplitude modulation by using a plurality of antennas, each coupled to a MIM load.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0048] Some of the specific details and values in the following detailed description refer to certain examples of the disclosure. However, this description is provided only by way of example and is not intended to limit the scope of the invention in any way. As will be appreciated by those skilled in the art, the claimed method and device may be implemented by using other methods that are known in the art per se. In addition, the described embodiments comprise different steps, not all of which are required in all embodiments of the invention. The scope of the invention can be summarized by referring to the appended claims.

[0049] The following description relates to a method and an apparatus for implementing a unique and innovative approach of light modulation. The approach demonstrated in the following description is based on loading the propagating electromagnetic field, rather than on switching the light source on and off. The loading of the electromagnetic field is done by placing one or more antennas in the field, and actively changing its loading. Thus, actively changing the impedance matching between the antenna and the medium, and consequently changing the power being transferred between. the medium and the antenna(s).

[0050] Let us now consider a setup, where an antenna is placed in a medium where an electromagnetic wave is propagating.

[0051] Assuming that the antenna is properly designed, the electromagnetic wave will induce AC currents across the antenna, as propagates therethrough.

[0052] Next, the energy balance of this setup is analyzed. To do so, let us consider the following two extreme scenarios: [0053] Scenario 1: the antenna is loaded using a perfect open. or short load. Open or short loads cannot consume any electrical energy, and accordingly, the currents being induced across the antenna arms will not impose any electrical energy on the load. In this case, the antenna may either reflect the energy back (i.e. a reflection mechanism) or would allow the electromagnetic energy to propagate through (i.e. a transmission mechanism). However, in both cases, all energy will remain within the electromagnetic field. This scenario is presented in FIG. 3, for a case where the antenna is open and transmits the energy therethrough.

[0054] Scenario 2: the antenna is loaded with a perfectly matched load. The term a perfectly matched load as used herein is used to denote a load that would cause absorption of all the electromagnetic energy picked by the antenna. In this case, the antenna absorbs the energy it has picked (i.e. absorption mechanism), and consequently the propagating electromagnetic field energy would be decreased by the very same amount of energy that was picked by the antenna. This scenario is presented in FIG. 4, for a case where the antenna is perfectly loaded and absorbs a significant portion of the energy through it.

[0055] A basic principle of the proposed solution relies on coupling one or more antennas to the electromagnetic field while allowing the electromagnetic waves to propagate along a waveguide. As the wave propagates, it is coupled to the antenna(s) along the waveguide. When coupled to the antenna(s), the electromagnetic wave may either go through or be reflected (it would go through for example, if the antenna(s) is/are not properly loaded, and would be reflected to the electromagnetic field either under open or short load conditions); or be absorbed by the antenna(s), if it/they is/are properly loaded.

[0056] Changing the electrical loading of the antenna(s), allows to amplitude modulate the electromagnetic field, as will be further explained.

[0057] An antenna coupled to a non-linear electrical load, may reflect different electro-magnetic loads by changing the DC bias of the non-linear load, for example, in case where an antenna coupled to a Metal-Insulator-Metal (MIM) structure, is used. MIM devices are well known in the art. They are two-port passive electrical devices, where two metals are separated from each other by a thin insulator. As voltage is applied across the metals, current appears to flow through the insulator utilizing the effect called tunneling effect. It can be shown that tunneling is a non-linear effect (as the current increases exponentially as a result of a linear increase in the voltage), and thus a MIM acts as a non-linear electrical load.

[0058] When coupling a MIM device (structure) to an antenna feed point, the loading perceived by the antenna is the differential load (dV/dI) as reflected by the MIM device. It can be shown that by DC biasing the MIM structure, different loads shall be reflected to the antennahence different impedance matching points are formed. FIG. 5 illustrates a typical differential resistance of a MIM structure, versus its DC bias voltage. As may be seen in FIG. 5, the impedance reflected by a MIM device may be changed by about 20% if one switches the DC bias point between 0 Volts and 100 mVolts.

[0059] FIG. 6 illustrates an embodiment of the invention of a system (10) for carrying out an amplitude modulation by using a single antenna (20) coupled to a MIM load (30). As the electromagnetic wave propagates along the waveguide (40), it comes across the antenna. The antenna load is formed by the use of the MIM (represented as a diode in FIGS. 6 and 7). The MIM is DC biased by an electrical modulating signal, generated by a modulating signal generator (50), and presents two possible loads to the antennabased on the DC voltage across it (as may be seen for example in FIG. 5). Accordingly, the electromagnetic field amplitude is modulated, based on the impedance matching between the antenna and the MIM load. The inductors in series (60) represents chokes, used to block the signal picked by the antenna from reaching the leads of the modulating signal source. Typically, these chokes are inherently built into the system, as part of the overall topology of the conductors.

[0060] FIG. 7 demonstrates another embodiment of the invention of a system for carrying out an amplitude modulation by using a plurality of antennas coupled to a MIM load, wherein the antennas are arranged serially along the waveguide. In this FIG., a series of antennas is illustrated, where each antenna is coupled to its own MIM load. All antenna loads are modulated in unison, with a single modulating signal. As the electromagnetic wave propagates through the waveguide, it is modulated by each of the antennas, in series. Such a topology yields a much better pronounced modulation depth, even if a single antenna does not reflect a perfect load to the signal. For example: if each antenna modulates only 2% of the signal (i.e. the best impedance match will only pick 2% of the signal), a sequence of 100 antennas will still yield a total modulation depth of 0.98100=13.2%.

[0061] There are certain advantages that are associated with the solution described hereinabove, when compared with prior art OOK type of modulation schemes. Some of the main advantages are the following: [0062] Energy consumption: the proposed scheme presents a major saving in power consumption when compared to existing OOK modulation schemes, as clearly demonstrated in the following Table 1:

TABLE-US-00001 TABLE 1 Antenna coupled MIM Laser switching modulator modulator Rate Hz 1.00E+10 1.00E+10 Capacitance F 1.00E17 1.00E12 V+ V 0.1 2.5 V V 0 0.7 V V 0.1 1.8 Resistance 100 10 Power Consumption mW 0.05 194.40 [0063] Production cost: Antenna coupled MIM structures are thin film products, which may be fabricated by using a standard semiconductors technology. Implementing an OOK modulator with the proposed technology is substantially cheaper than using modulators which are known in the art per se. [0064] Integration: the proposed solution can be easily integrated with semiconductor and silicon photonics based products. Integrated solutions are cheaper, and present lower parasitic elementsthus even more efficient power consumption.

[0065] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein, for example cases where the optical signals are conveyed to the antenna via a waveguide/optical fiber in the addition or in the alternative of being conveyed in free space. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.